Quasi in-situ study of morphological evolution of the interfacial IMC in single-sided interface Sn-0.3Ag-0.7Cu/Cu joints during multiple reflow process

In electronic packaging, the interfacial IMC of solder interconnects (or joints) has long been recognized as an important factor influencing the reliability of solder joints. In this study, a novel quasi in-situ method is proposed to achieve the continual observation of morphological evolution and growth of the interfacial IMC grains in single-sided interface Sn-0.3Ag-0.7Cu/Cu joints undergoing multiple reflow soldering process. Results show that the scallop-like Cu6Sn5 grains exhibits a surface morphology change from the protruding to flat against the number of reflow cycles, and the interfacial IMC grains grow significantly as the reflowing time is prolonged or the reflow temperature is increased. The growth of interfacial Cu6Sn5 grains in SAC0307/Cu joints shows the characteristics described by the theory of Ostwald ripening, in which some large grains grow rapidly while some small grains neighboring the growing large grains disappear. The interfacial IMC grains with the ripening growth behavior locate mainly near the Cu substrate, and the ripening behavior of IMC grains is always accompanied with the interfacial reaction growth behavior throughout the entire reflow process.